I started Aikido under Ikeda sensei almost 20 years ago and he has been my teacher ever since. In hindsight I see several general phases to what he has focused on in his teaching.

At the time I started he was in a generating/amplifying power phase, mostly through hip/body movement "koshi power". Back then you really got an appreciation for just how hard sensei can throw when he feels like it.

As he began doing more and more seminars his teaching focused on connecting to and manipulating the uke through complex spiral movements. Basically combining koshi power with balance breaking.

Upon meeting Ushiro sensei, Ikeda sensei undertook a deep and focused study of internal work. The earlier balance breaking was something done to the uke, where the internal balance breaking is something done within the nage, making it more subtle (hidden even) and difficult to resist. Removing the uke's power rather than generating nage power. I would guess 4 years or so were spent in this stage.

My take on what sensei has been doing for the last year is taking the internal work and now applying it back to the earlier stages. So a lot more application of internal into familiar techniques, internal combined with koshi power, basically folding the new stuff back into old. Also I think through the laboratory of his seminars he has been adjusting and refining how to transmit the internal work.

I think one of the more common problems people have in picking up what he is showing is that they don't take him literally when they should. Between the language barrier, and just a lack of a common vocabulary when discussing concept I think it's tempting to think that he's talking in metaphor when sometimes he is not.

When he was first talking about "change your insides" I was baffled as to what that meant. Then at a break during a seminar we were having some coffee and in response to one of my questions he asked me to put a hand on his shoulder. Because he was wearing a t-shirt instead of a loose fitting dogi I was able to see his abdomen actually moving around as he took my stability away. So when he says change your insides, he actually means (at least in part) to move your abdominal organs into a different position.

Knowing that and doing it are of course two different things. I know I could wiggle my ears but I haven't worked out quite how to do it even though they say 15 minutes in front on a mirror will do it. I think for a lot of people they don't have a system for learning how to move their insides around. I have exercises that I've picked up from Systema for working internally with strikes that I have found work very well. It sounds like the Daito Ryu folks and others have their own approaches as well (check out some belly dancing tutorials on YouTube, impressive stuff). The comments from several people about schools' teachers needing to prep their students for Ikeda sensei's work are spot on in my opinion.

Ikeda sensei already had the physical ability and control that he could apply to Ushiro sensei's approach, so he was able to skip over a phase that many of us require. He not just doing advanced work, he's doing advanced-advanced work. I think we'll see more exercises from him to address the development of internal coordination as part of his presentation in the future.

Finally, a comment on the title of this thread. Ikeda sensei has always intentionally avoided using the word "ki" in his teaching and discussions of Aikido. I think I finally heard it for the first time last year, and it was a surprise to me. In it's place he always used the word "energy" - I believe because he wanted to distance what he's doing from any kind of mysticism or magic. Even when something can't be explained, I think he would assert that there's some combination of subtle physical and psychological principles at play.

Any time there are non-Aikido people at a seminar, like some Karate students who sat in on some of his classes at the Expo, he has used them for ukemi as much as possible. He knows that there are people skeptical of the internal work, that seeing it looks fake, and that feeling it is the only way to really get an appreciation for it. Luckily he is very receptive to questions and letting people feel his work first hand.

To pass along one comment, my own internal movement was originally tied to my breathing. I think it's easier to pick up that way, but in discussing it with sensei he clearly stated that the internal work is independent of breath. So kokyu might start you down the path, but it's something you should eventually be able to drop.